Pumps capable of handling fluids such as water that includes solids are known in the prior art. One type of pump that is capable of handling solids is termed a “vortex” pump. An example of such a pump is disclosed in U.S. Pat. No. 4,676,718. Centrifugal pumps such as disclosed in U.S. Pat. Nos. 3,898,014 and 6,887,034, which are hereby incorporated by reference, are also capable of handling solids in waste water pumping applications.
Pumps capable of passing relatively large solids, such as vortex pumps, characteristically have high flow rates at low head pressures. In the marketplace, it has been found that it is desirable to have pumps that can operate at higher head pressures at low flow rates, without sacrificing solids handling capability. Attempts at designing and making pumps capable of producing higher head pressures at low flow rates have been made. It has been found however, in some applications, that these types of pumps tend to require larger size motors to prevent overloading the motor in a high flow application.